Stabilized non-polymeric acetoacetate esters that promote adhesion to metallic and oxidized substrates

ABSTRACT

The present invention provides improved adhesion promoters for latex paints. The adhesion promoters are enamines of acetoacetate esters, or substituted acetoacetate esters. The invention also provides two new compounds which are useful as adhesion promoters: 2-butyl-2-ethyl-1,3-propanediol bis(3-amino-2-butenoate) and trimethyl propane tris(3-amino-2-butenoate), and which are stable to hydrolysis on prolonged storage.

This is a Divisional application of application Ser. No. 08/944,654,filed Oct. 6, 1997, now U.S. Pat. No. 5,913,970.

FIELD OF THE INVENTION

The present invention is directed to waterborne coating compositionscontaining an aqueous polymer dispersion and a non-polymeric materialwhich improves adhesion to metal substrates.

BACKGROUND OF THE INVENTION

Waterborne coatings comprise a polymeric material dispersed or dissolvedin an aqueous medium. When a waterborne coating is applied to asubstrate and dried, the polymeric material forms a film which protectsthe substrate. Certain additives such as coalescing agents orplasticizers are frequently used to promote coalescence of the latexparticles in the coating during film formation so that the resultingfilm has a smooth glossy appearance and completely covers and protectsthe substrate. Other additives are used to improve the adhesion of thecoating film, especially on metal substrates.

U.S. Pat. Nos. 4,296,226 and 4,421,889 teach that polymers havingacetoacetyl pendant groups provide for improved adhesion to smoothnon-absorbent surfaces. Further, U.S. Pat. No. 5,055,511 and 5,120,607describe the use of acetoacetylated acrylic polymers in mastic caulkingcompositions. Other patents, such as U.S. Pat. No. 5,002,998, U.S. Pat.No. 4,292,661, EP 390,370, EP 262,720 and EP 326,723, and Japanese KokaiHei 4 (1992)-154873 describe the use of polymers containing acetoacetoxygroups bound to the polymeric structure. Further, U.S. Pat. No.5,349,026 describes the use of a polymer, containing an acetoacetategroup, in a coating or impregnating composition. The polymer functionsto coalesce and crosslink an emulsion polymer. U.S. Pat. No. 5,494,975describes preparation of polymers containing functional acetoacetategroups which are then reacted with a functional amine to form anenamine.

European Patent Application 262,720 refers to the use of polymers whichcontain pendant acetoacetoxy groups as adhesion promoters and furtherdiscloses that these polymers protect the acetoacetoxy moieties fromhydrolyzing by adding a sufficient amount of ammonia or amine to convertthe acetoacetoxy moieties to the corresponding enamines.

In all of the above references, the acetoacetoxy group is chemicallybound to the polymer which forms the coating. This severely limits thechemical nature of the polymeric coating, since the polymer must eitherbe based upon an acetoacetylated copolymerizable monomer or it mustcontain pendant groups, such as hydroxy or amine, which are capable ofreacting with an acetoacetylating agent.

Japanese Patent 3,290,486 describes a process for promoting adhesion toa tin-lead alloy plated steel sheet which involves immersing the sheetin an aqueous acetoacetic acid ester prior to painting.

SUMMARY OF THE INVENTION

The present invention provides a method for improving the adhesion ofwaterborne coating compositions to various substrates, especially torusty, corroded or galvanized metals. The invention also provideswaterborne coating compositions comprising an aqueous polymerdispersion, an enamine component and, optional conventional additives.The waterborne compositions have improved adhesion to substrates,particularly to rusty, corroded and galvanized metal surfaces.

A further aspect of the present invention is the discovery of two novelcompounds, 2-butyl-2-ethyl-1,3-propanediol bis(3-amino-2-butenoate) andtrimethylpropane tris(3-amino-2-butenoate), which also improve adhesionof waterborne coatings to substrates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Applicants have unexpectedly found that when a non-polymeric enamine isadded to waterborne coating compositions either as a pure compound or asa solution or as a dispersion, in the presence of other conventionalpaint additives such as coalescing aids, adhesion of the waterbornecoating composition to a substrate is enhanced. Further, the enamine ofthe present invention may be added to the waterborne composition duringformulation of the aqueous polymer composition or just prior toapplication of the formulation onto a substrate. The resultingwaterborne composition has the desirable properties of the base polymercomposition, however, in addition, exhibits greatly improved adhesion,especially to corroded metal and oxidized substrates.

Thus, the present invention provides waterborne compositions comprising:(A) an aqueous dispersion polymer, and (B) a compound of formula (I)which is represented by a number of tautomeric and isomeric forms suchas:

    (R.sup.1 C(═NR.sup.3)CHR.sup.4 COO).sub.x R.sup.2 ⃡(R.sup.1 C(NR.sup.3 R.sup.4)═CHCOO).sub.x R.sup.2              (I)

where R¹ and R² are independently C₁ -C₅ alkyl groups or the residue ofa polyol, either or both of R³ and R⁴ are hydrogen or C₁ -C₅ alkylgroups, and x is an integer of from 1 to 3.

Component (A)--Aqueous Dispersion Polymer

Useful aqueous dispersion polymers for practice of the present inventionmay be selected from an acrylic latex, a vinyl polymer and a water-bornealkyd. Preferably, the aqueous dispersion polymer of the presentinvention is an acrylic latex polymer or vinyl latex polymer formed bycopolymerization of known monoethylenically unsaturated monomers. Theterm "latex" is used in the conventional meaning to denote stabledispersions of resin particles in a water system. Further, the term"polymer" is used to denote a homopolymer or a copolymer.

Suitable polymerizable or copolymerizable monoethylenically unsaturatedmonomers for the preparation of a latex polymer include, but are notlimited to, a monoethylenically unsaturated monomer which may berepresented by the general Formula (II):

    CH.sub.2 ═C(R.sup.3)COOR.sup.4                         (II)

where R³ is hydrogen or a C₁ -C₃ alkyl group, and R⁴ is a C₁ -C₂₀ alkylgroup, phenyl, benzyl, hydroxy-(C₁ -C₄)-alkyl, alkoxy-(C₁ -C₄)-alkyl,cyclopentyl, cyclohexyl, C₁ -C₄ -alkylfuryl, tetrahydrofuryl, C₁ -C₄alkyltetrahydrofuryl and combinations of these monomers thereof.Combinations of monomers where R³ is hydrogen and monomers where R³ isan alkyl group are used to modify the glass transition temperature ofthe latex polymer.

Preferred examples of comonomers are, but are not limited to, methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl(meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl(meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl(meth)acrylate, stearyl (meth)acrylate, phenoxyethyl (meth)acrylate,methoxyethyl (meth)acrylate, benzyl (meth)acrylate, ethoxyethyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclopentyl (meth)acrylate,and isobornyl (meth)acrylate, as well as combinations of those monomersthereof. The term "(meth)acrylate" is used to denote an acrylate ormethacrylate. The term "alkyl" is used to denote straight chain orbranched alkyl groups.

Additional suitable monoethylenically unsaturated monomers includestyrenic monomers. Styrenic monomers denote styrene, or a substitutedstyrene, such as C₁ -C₆ alkyl ring-substituted styrene, C₁ -C₃alkyl-substituted styrene or a combination of ring and -alkylsubstituted styrene. Preferred styrenic copolymerizable monomers includestyrene, p-methyl styrene, o-methyl styrene, -methyl styrene andcombinations thereof.

In addition, vinyl ester monomers may be used as monoethylenicallyunsaturated monomers. Such vinyl esters include vinyl acetate,di-n-butylmaleate, and compounds of the general Formula (III):

    CH.sub.2 ═CH--OC(═O)--(C--(R.sup.5).sub.2).sub.n   (III)

where R⁵ is a hydrogen or a C₁ -C₁₂ alkyl group and where n is aninteger of 1 to 20; preferably at least one R⁵ is methyl.

The latex polymers referred to herein are known polymers. Latex polymerscan be prepared by conventional free radical emulsion polymerizationprocesses known in the art. Conventional catalysts used in emulsionpolymerization include hydrogen peroxide, potassium or ammoniumperoxidisulfate, dibenzoyl peroxide, lauryl peroxide, ditertiarybutylperoxide, 2,2'-azobisisobutyronitrile, t-butyl peroxide, t-butylhydroperoxide, benzoyl peroxide, sodium formaldehyde sulfoxylate and thelike.

Suitable surfactants for the preparation of latex polymers includeanionic or nonionic surfactants, such as alkylpolyglycol ethers,including ethoxylation products of lauryl, oleyl, and stearyl alcohols;alkylphenolpolyglycol ethers, such as ethoxylation products of octyl- ornonylphenol, diisopropylphenol, triisopropylphenol; alkali metalammonium salts or alkyl, aryl or alkylaryl sulfonates, sulfates,phosphates, and the like, including sodium lauryl sulfate, sodiumoctylphenol glycol ether sulfate, sodium dodecylbenzene sulfonate,sodium lauryl diglycol sulfate, ammonium tri-tertiary butyl phenolsulfonate, and penta- and octa-glycol sulfonates; sulfosuccinate saltssuch as disodium ethoxylated nonylphenol, half ester or sulfosuccinicacid, disodium n-octyldecyl sulfosuccinate, sodium dioctylsulfosuccinate, and the like. The term "aryl" in the context of thisapplication is used to denote an aromatic ring radical or a substitutedaromatic ring radical, such as phenyl, naphthyl or anthracenyl radical.

In addition, reactive anionic or nonionic surfactants possessing styreneor allyl groups may be used in the preparation of latex polymers.Examples include surface active monomers such as SAM 181, 183, 184, 211,sold by PPG Industries, Inc., which are anionic sulfates or sulfonates,and SAM 185-187 which are nonionic reactive surfactants. Other reactivesurfactants include those sold by Daiichi Kogyo Seiyaku under the nameAQUARON surfactant.

Examples of AQUARON surfactants include compounds of the formulae:##STR1## wherein R⁶ is C₁ -C₁₂ alkyl group and m is an integer of from 1to 5. Additional reactive surfactants include sodium alkyl allylsulfosuccinate, sold by Henkel under the tradename TREM LF40 surfactant.Further examples of such surfactants can be found in U.S. Pat. Nos.5,185,212; 2,600,831; 2,271,622; 2,271,623; 2,275,727; 2,787,604;2,816,920; and 2,739,891, incorporated herein by reference.

Alternatively, the aqueous suspension polymer can be waterborne alkyds.The term "alkyd" is used to denote a synthetic resin which is thecondensation product of polybasic acids, polyhydric alcohols and oilfatty acids. Such alkyds are generally prepared by polycondensation ofvarious polybasic acids, polyhydric alcohols and fatty acids. The term"oil fatty acid" as used herein denotes, for example, tall oil fattyacid (TOFA), linseed oil, soybean oil, coconut oil, castor oil,sunflower oil, safflower oil, tung oil, oiticia oil, etc. These oilscontain both saturated and unsaturated fatty acids. Depending on oiltype and composition, the saturated fatty acid content varies in therange of from about 2.0 to 95.0 weight %, whereas the unsaturated fattyacid content varies from about 10.0 to about 98.0 wt. %.

The saturated fatty acid content in these oils is mainly from a mixtureof stearic (C₁₈) and palmitic (C₁₆) acids, but various oils containingsaturated fatty acids with C₈, C₁₀, C₁₄ carbon chain may also be used.The unsaturated fatty acid content in these oils is mainly from oleicacid, linoleic acid and linolenic acid.

Polyhydric alcohols used in the preparation of waterborne alkyds includeglycerol, neopentyl glycol (NPG), cyclohexanedimethanol (CHDM), ethyleneglycol, propylene glycol, pentaerythritol, neononyl glycol (NNG),diethylene glycol (DEG), dipropylene glycol (DPG), trimethyl pentanediol(TMPD), triethylene glycol (TEG), trimethylolpropane (TMP),dipentaerythritol (DPE), tripentaerythritol (TPE) and the like.

Polybasic acids used in the preparation of waterborne alkyds include,but are not limited to, cyclohexanedicarboxylic acid (CHDA), isophthalicacid (IPA), terephthalic acid (TPA), phthalic anhydride (PA), adipicacid (AD), oxalic acid, malonic acid, dimethylmalonic acid, succinicacid, glutaric acid, trimethyladipic acid, pimelic acid,2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid,maleic acid, itaconic acid, 2,5-norbornane dicarboxylic acid,1,4-naphthalic acid, diphenic acid, 4,4'-oxydibenzoic acid, diglycolicacid, thiodipropionic acid, 4,4'-oxydibenzoic acid, diglycolic acid,thiodipropionic acid, 4,4'-sulfonyldibenzoic acid,4,4'-diphenyldicarboxylic acid, and 2,6-naphthalene dicarboxylic acid.Suitable dicarboxylic acids used in waterborne alkyds include aliphaticdicarboxylic acids, aromatic dicarboxylic acids, alicyclic dicarboxylicacids or mixtures of two or more of these acids. Examples ofcommercially available waterborne alkyds include AROLON resin, availablefrom Reichhold. Further examples may be found in the treatise by C. R.Martens, in "Alkyd Resins", Reinhold Publishing Corp., New York, 1961.

Acetoacetate compounds useful in the practice of the present inventionmay be prepared by methods known in the art, such as those described inU.S. Pat. No. 5,051,529, incorporated herein by reference.

In the above described waterborne compositions, the aqueous dispersionpolymer may preferably have a particle size of from about 0.01 to about3 microns, as measured by electron microscopy. The polymer particlesgenerally have a spherical shape. In a preferred embodiment, thespherical polymeric particle has a core portion and a shell portion or agradient structure. Conventionally, in core/shell particles the Tg ofthe polymer composition of the core is different from the Tg of thepolymer composition of the shell. The core/shell polymer particles mayalso be prepared in a multi-lobe form, a peanut shell, an acorn form, araspberry form or any other form.

The glass transition temperature (Tg) of the aqueous dispersion polymer,in accordance with the present invention, may be up to about 100° C. Ina preferred embodiment of the present invention, where film forming atambient temperatures is desirable, the glass transition temperature maypreferably be under 60° C.

It should be understood that the only limitation on the aqueousdispersion polymer is that it is one in which the polymer contains nofunctional groups which are reactive with component (B), an enamine. Itis preferred that the polymer component (A) does not contain a pendantfunctionality or formula of an enamine, either by copolymerization witha monomer containing such functionalities or by a post reaction tointroduce pendant acetoacetate functionalities of formula (IV):

    --(R.sup.1 C(═O)CH.sub.2 COO).sub.x R.sup.2            (IV)

where R¹, R² and x are as defined in formula (I), which might react toform an enamine.

Component (B)--Enamine Compound

Component (B) is an enamine which is not chemically bound to the aqueouspolymer dispersion (A). Component (B) is a compound represented byformula (I):

    (R.sup.1 C(NR.sup.3 R.sup.4)═CHCOO).sub.x R.sup.2      (I)

It is further understood that formula (I) may exist in the followingform:

    (R.sup.1 C(═NR.sup.3)CHR.sup.4 COO).sub.x R.sup.2

Thus, formula (I) represents both tautomeric and isomeric forms of anenamine. The term "enamine" is used to denote a reaction product of anacetoacetic acid ester with a primary or secondary amine according tothe following equation

    R.sup.1 C(═O)CH.sub.2 COOR.sup.2 +R.sup.3 R.sup.4 NH--H.sub.2 O→R.sup.1 C(NR.sup.3 R.sup.4)═CHCOOR.sup.2 ⃡R.sup.1 C(═NR.sup.3)CHR.sup.4 COOR.sup.2

where R¹ and R² are C₁ -C₅ alkyl groups as defined above and either orboth R³ and R⁴ are hydrogen or the same or different C₁ -C₅ alkylgroups. Further, if the amine is primary, R⁴ is hydrogen and thereaction product may exist in either of the tautomeric forms shown inthe above equation. On the other hand the reaction product of asecondary amine exists only in the enamine form.

Preferred compounds of Formula (I) include, but are not limited to,enamines of acetoacetate esters such as: the enamine of ethylene glycolbis(acetoacetate); the enamine of diethylene glycol bis(acetoacetate);the enamine of propylene glycol bis(acetoacetate); the enamine of2,2,4-trimethylene glycol bis(acetoacetate); the enamine ofcyclohexanediol bis(acetoacetate); the enamine of trimethylpropanetris(acetoacetate) and the enamine of glycerol tris(acetoacetate).Limitations of R¹ and R² are chiefly those imposed by the physicalcharacteristics such as melting point, volatility, solubility, etc., ofthe resulting ester. Examples of such compounds include, but are notlimited to, those where R¹ is methyl, R² is t-butyl, and x is 1; whereR¹ is methyl, R² is ethyl and x is 1; and where R¹ is ethyl, R² is butyland x is 1. Further, either or both of R¹ and R² may contain othersubstituents, so long as component (B) contains no substituents that arereactive with component (A) to which they are added and does notadversely affect the substrate to which they are applied.

The amount of component (B) required to produce the desired adhesionpromoting effect will depend upon a number of factors, such as thedegree of corrosion of the metal substrate or other pretreatment towhich the substrate has been subjected. In general, the preferred rangeis from 1 to 25 parts by weight of component (B) per 100 parts by weight(phr) of aqueous polymer dispersion component (A); a more preferredrange is from 10 to 25 phr; and most preferred is from 15 to 20 phr. Theupper concentration of component (B) may be limited both by economicconsiderations and because incremental improvement may be slight atconcentrations of component (B) above about 25 phr.

In a further aspect of the present invention, where the acetoacetateester is derived from 2-butyl-2-ethyl-1,3-propane diol or fromtrimethylpropane, and the amine is ammonia, the products, namely,2-butyl-2-ethyl-1,3-propanediol bis(3-amino-2-butenoate) andtrimethylpropane tris(3-amino-2-butenoate), respectively, are newcompositions of matter useful in the present invention for promotingadhesion of waterborne compositions to various substrates.

Component C--Additives

Components (A) and (B) of this invention may be used in combination withother optional conventional paint additives, such as coalescing aids,dryers, pigments, surfactants, and the like.

Included among such additives are leveling, rheology, and flow controlagents such as silicones, fluorocarbons or cellulosics; flatting agents;pigment wetting and dispersing agents and surfactants; ultraviolet (UV)absorbers; UV light stabilizers; tinting pigments; defoaming andantifoaming agents; anti-settling, anti-sag and bodying agents;anti-skinning agents; anti-flooding and anti-floating agents; fungicidesand mildewcides; corrosion inhibitors; thickening agents; or coalescingagents.

Specific examples of such additives can be found in "Raw MaterialsIndex", published by the National Paint & Coatings Association, 1500Rhode Island Avenue, N.W., Washington, D.C. 20005.

Examples of flatting agents include SYLOID® synthetic silica, availablefrom the Davison Chemical Division of W.R. Grace & Company; HERCOFLAT®polypropylene, available from Hercules Inc.; and ZEOLEX® syntheticsilicate, available from J.M. Huber Corporation.

Examples of dispersing agents and surfactants include sodiumbis(tridecyl) sulfosuccinnate, di(2-ethyl hexyl) sodium sulfosuccinnate,sodium dihexylsulfosuccinnate, sodium dicyclohexyl sulfosuccinnate,diamyl sodium sulfosuccinnate, sodium diisobutyl sulfosuccinnate,disodium iso-decyl sulfosuccinnate, disodium ethoxylated alcohol halfester of sulfosuccinnic acid, disodium alkyl amido polyethoxysulfosuccinnate, tetrasodium N-(1,2-dicarboxy-ethyl)-N-oxtadecylsulfosuccinnamate, disodium N-octasulfosuccinnamate, sulfatedethoxylated nonylphenol, 2-amino-2-methyl-1-propanol, and the like.

Examples of viscosity, suspension, and flow control agents includepolyaminoamide phosphate, high molecular weight carboxylic acid salts ofpolyamine amides, and alkylene amine salts of an unsaturated fatty acid,all available from BYK Chemie U.S.A. under the tradename ANTI TERRA®wetting agent. Further examples include polysiloxane copolymers, aqueouspolyacrylate solution, cellulose esters, hydroxyethyl cellulose,hydrophobically-modified hydroxyethyl cellulose, hydroxypropylcellulose, polyamide wax, polyolefin wax, carboxymethyl cellulose,ammonium polyacrylate, sodium polyacrylate, and polyethylene oxide.Examples of thickeners include the methane ethylene oxide associativethickeners and water soluble carboxylated thickeners, for example, UCAR45 water soluble carboxylated thickener available from by Union Carbide.

Several proprietary antifoaming agents are commercially available, forexample, under the tradename BRUBREAK of Buckman Laboratories Inc.,under the BYK® tradename of BYK Chemie, U.S.A., under the FOAMASTER® andNOPCO® tradenames of Henkel Corp./Coating Chemicals, under the DREWPLUS®tradename of the Drew Industrial Division of Ashland Chemical Company,under the TROYSOL® and TROYKYD® tradenames of Troy Chemical Corporation,and under the SAG® tradename of Union Carbide Corporation.

Examples of fungicides, mildewcides, and biocides include4,4-dimethyloxazolidine, 3,4,4-trimethyl-oxazolidine, modified bariummetaborate, potassium N-hydroxy-methyl-N-methyldithiocarbamate,2-(thiocyanomethylthio)benzothiazole, potassium dimethyldithiocarbamate, adamantane, N-(trichloromethylthio)phthalimide,2,4,5,6-tetrachloroisophthalonitrile, orthophenyl phenol,2,4,5-trichlorophenol, dehydroacetic acid, copper naphthenate, copperoctoate, organic arsenic, tributyl tin oxide, zinc naphthenate, andcopper 8-quinolinate.

Further, examples of useful conventional additives (C) can be found in"Raw Materials Index", published by the National Paint & CoatingsAssociation, 1500 Rhode Island Avenue, N.W., Washington, D.C. 20005.

Examples of U.V. absorbers and U.V. light stabilizers includesubstituted benzophenone, substituted benzotriazoles, hindered amines,and hindered benzoates, available from American Cyanamide Company underthe tradename CYASORB UV, anddiethyl-3-acetyl-4-hydroxybenzyl-phosphonate, 4-dodecyloxy-2-hydroxybenzophenone, and resorcinol monobenzoate.

The paint or coating additives described above form a relatively minorproportion of the waterborne composition of the present invention,Additive component (C) may be present in an amount from about 0.05 wt. %to about 5.00 wt. %, based on the total weight of components (A) and (B)of the waterborne composition. However, the amount of additives is notcritical and may be adjusted higher or lower to obtain desiredproperties.

The waterborne composition as set forth above, may further comprises oneor more pigments in a concentration of about 1 to about 70 wt. %,preferably about 30 to about 60 wt. % based on the total weight ofcomponents (A) and (B) in the waterborne composition.

Pigments suitable for use in the coating compositions envisioned by thepresent invention are typically organic and inorganic pigments,well-known to one of ordinary skill in the art of surface coatings.Examples include, but are not limited to the following: CI Pigment White6 titanium dioxide; CI Pigment Red 101 red iron oxide; CI Pigment Yellow42, CI Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, all copperphthalocyanines; CI Pigment Red 49:1; and CI Pigment Red 57:1.

After formulation, the waterborne composition may then be applied to adesired substrate or article, e.g., steel, aluminum, or galvanizedsheeting (either primed or unprimed), and allowed to air dry. Awaterborne composition in accordance with the present invention mayfurther be designed for industrial coatings, textile coatings, inkcoatings, adhesives, or coatings for plastics. While the compositions ofthe invention are preferentially applied as coatings for rusty orcorroded metal substrates, it should be understood that the waterbornecoating compositions are adhesion promoters and may also be broadlyapplicable to other substrates. Thus, as a further aspect of the presentinvention, there is provided a method for coating a shaped or formedarticle with the waterborne compositions of the present invention.

Although the invention is described in the Examples that followparticularly with reference to rusted or Bonderized™ steel, it should beunderstood that they are also applicable to cleaned and treated metal orto metal which has been subjected to other treatments, such asgalvanizing or treating with other surface coatings. Use of thecomposition of the present invention on various iron alloys, in additionto steel, is also within the scope of the present invention.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

EXAMPLES

Test Methods

Metal Pretreatment

Cold rolled steel was used as the substrate in all of the examples.Unless specified otherwise, the steel was subjected to treatment withBONDERITE™ 1000 iron phosphate wash. For evaluation on "rusted" steel,cold rolled steel was "rusted" by treatment in a salt fog chamber for 96hours and washed to remove traces of salt.

Adhesion to Substrates

Adhesion was evaluated by the "Cross-Cut Tape Test" described in ASTM3359-87, "Standard Test Methods for Measuring Adhesion by Tape Test",using a Gardner Cross Hatch Adhesion Tester. The grid was covered withpressure sensitive tape, which was smoothed by hand to ensure goodcontact, and then removed by a rapid pulling motion. The degree ofadhesion of the coating was rated from the damage to the grid andreported in the following tables as percentage of paint squares whichremained intact.

Salt Fog Test

This test was run according to ASTM Method B117-90, in which salt fogwas allowed to deposit on the test paneling in a closed chamber, afterwhich the panel was examined visually and, if desired, subjected toother tests.

Component (A)--Aqueous Dispersion Polymer

The following resins were used in the examples: NEOCRYL® acrylic-styreneresin, a registered trade mark of ICI; RHOPLEX® acrylic resin, aregistered trade mark of Rohm and Haas; and AROLON® water dispersiblealkyd resin, a registered trade mark of Reichhold.

Example 1

This example illustrates the preparation of the "enamine",2-butyl-2-ethyl-1,3-propanediol bis(3-amino-2-butenoate).

Aqueous ammonium hydroxide (9.54 g of 28% solution) was added drop wise,with stirring, to 3 g of 2-butyl-2-ethyl-1,3-propanediol and theresulting mixture was stirred vigorously for about 2 minutes, thenallowed to stand for 48 hours. The product consisted of an oily toplayer, a lower aqueous layer, and a milky precipitate. The product wasextracted with methylene chloride and the organic layer washed withsaturated sodium chloride. The methylene chloride was removed by heatingon a rotary evaporator at 50° C. at 100 mm for 2 hours. Analysis of theproduct by H¹ NMR indicated that it contained the mono- and di-enaminesof 2-butyl-2-ethyl-1,3-propanediol bis(3-amino-2-butenoate).

Example 2

The above reaction was carried out using trimethylol propanetris(acetoacetate) to similarly yield trimethylolpropanetris(3-amino-2-butenoate), the identity of which was confirmed by H¹NMR.

Example 3

This example illustrates the preparation of ethyl 3-amino-2-butenoateand its use as an adhesion promoter.

A mixture of 60 g of ethyl acetoacetate and 222 g of ammonium hydroxidewas shaken vigorously in a separatory funnel and the resulting lower,oil, layer of ethyl 3-amino-2-butanoate was removed. This material (5 g)was then added to 50 g of NEOCRYL® A650 acrylicstyrene resin, with thepH adjusted to about 9.8 by addition of ammonium hydroxide. The mixturewas placed on a roller for 8 hours to mix thoroughly, then coated ontoBonderite™ 1000 cold rolled steel panels to give approximately 3 milfilms. After curing the coating was evaluated by the cross hatchadhesion test described above. The film showed 100% retention of thecoating. In contrast, a control film of NEOCRYL® A650 acrylic-styreneresin, which did not contain the enamine, showed 0% retention of thecoating.

Example 4

An identical experiment described in Example 3 was carried out usingtertiary butyl-3-amino-2-butenoate. The film showed 100% retention ofthe coating.

Example 5

This example illustrates the use of ethyl-3-amino-2-butanoate to improvethe adhesion of a waterborne epoxy enamel, an enamel which normallyexhibits poor early adhesion to steel.

An epoxy enamel was used as received from the manufacturer and containedTRU-GLAZE™ epoxy #12949-01 and #12902-01. A sample of this material wasmixed with a small amount of ethyl 3-amino-2-butanoate and the productwas coated onto Bonderite™ 1000 treated cold rolled steel and cured for3 hours at 50° C. The resulting coating showed 100% retention of thecoating in the cross hatch adhesion test described above. In contrast, asimilar coating made from the enamel without added enamine showed lessthan 50% retention of the coating.

Example 6

This example illustrates the preparation of coatings utilizing theacetoacetate enamine as a hydrolytically stable form of acetoacetate foradhesion promotion.

Coating compositions were prepared according to Table 1 below. Thecoating compositions containing the waterborne latex were placed on aroller for 8 hours to mix, then coated onto Bonderite™ 1000 cold rolledsteel to give about 3 mil wet films. After curing, the coatings wereevaluated by the cross hatch adhesion test described above. Theseresults are shown in Table 2. All the films of the present inventionshowed 100% initial retention to the substrate. The coated samples werethen placed in an oven at 50° C. for 4 weeks, after which they werereevaluated for adhesion. These results are also shown in Table 2.

                  TABLE 1                                                         ______________________________________                                        COATINGS COMPOSITIONS                                                           Components  A      B      C    D      E    F                                ______________________________________                                        Neocryl A650                                                                             50 g   50 g     50 g                                                                              --     --   --                                   with NH.sub.4 OH                                                              (pH = 9.8)*                                                                   Neocryl A650 -- -- --  50 g  50 g  50 g                                       (pH = 6.3)                                                                    ethyl -- -- -- 5.6 g -- --                                                    acetoacetate                                                                  t-butyl -- -- -- -- 5.6 g --                                                  acetoacetate                                                                  BEPD bis -- -- -- -- -- 5.6                                                   acetoacetate                                                                  EAA enamine 5.0 g -- -- -- -- --                                              t-BAA enamine -- 5.0 g -- -- -- --                                            BEPD bis -- -- 5.0 g -- -- --                                                 enamine                                                                     ______________________________________                                         BEPD = 2butyl-2-ethyl-1,3-propane diol                                        EAA = Ethyl acetoacetate                                                      tBAA = tbutyl acetoacetate                                                    *NEOCRYL A650 has a pH of about 6.5. Ammonium hydroxide was used to adjus     the pH to 9.8 to help keep the acetoacetate enamine in the enamine form.      All aceotacetates (enamine or otherwise) were added at 25 parts by weight     per 100 parts of resin solids.                                           

                  TABLE 2                                                         ______________________________________                                        EVALUATION AND STABILITY OF COATINGS                                                            Initial     Final (4 Wks)                                      Cross Hatch Cross Hatch                                                      Components Adhesion Results Adhesion Results                                ______________________________________                                        Neocryl A650   0%          0%                                                   NH.sub.4 OH                                                                   (pH = 9.8                                                                     Neocryl A650  0%  0%                                                          (pH = 6.3)*                                                                   Ethyl 100%  0%                                                                Acetoacetate                                                                  t-Butyl 100% 100%                                                             Acetoacetate                                                                  BEPD bis 100% Gelled                                                          Acetoacetate                                                                  EAA Enamine 100% 100%                                                         t-BAA Enamine                                                                 BEPD bis 100% 100%                                                            Enamine                                                                     ______________________________________                                         *EKTASOLVE EB at 25 phr was used to coalesce the film.                        BEPD = 2butyl-2-ethyl-1,3-propane diol                                        EAA = ethyl acetoacetate                                                      tBAA = tbutyl acetoacetate                                               

The results show adhesion to the substrate remained at 100% retentionfor both the acetoacetate and enamine forms of both tertiary butylacetoacetate and 2-butyl-2-ethyl-1,3-propane diol. The otheracetoacetates showed loss of adhesion

Example 7

The latex coating formulations of Example 6 were observed for stabilityafter 4 weeks storage in an oven at 50° C. The observations are shownbelow in Table 3.

                  TABLE 3                                                         ______________________________________                                        STORAGE STABILITY STUDY AT 50° C.                                        Components Stability Observations                                           ______________________________________                                        Neocryl A650       None Expected                                                NH.sub.4 OH                                                                   (pH = 9.8                                                                     Neocryl A650 None Expected                                                    (pH = 6.3)*                                                                   Ethyl Popped and Fizzed                                                       Acetoacetate When Opened                                                      t-Butyl Popped and Fizzed                                                     Acetoacetate When Opened                                                      BEPD bis No Change Noted                                                      Acetoacetate                                                                  EAA Enamine Solid Lump in Liquid                                              t-BAA Enamine No Change Noted                                                 BEPD bis No Change Noted                                                      Enamine                                                                     ______________________________________                                         *EKTASOLVE EB at 25 phr was used to coalesce the film.                        BEPD = 2butyl-2-ethyl-1,3-propane diol                                        EAA = ethyl acetoacetate                                                      tBAA = tbutyl acetoacetate                                               

After 4 weeks aging, the latex compositions containing2-butyl-2-ethyl-1,3-propane diol bis acetoacetate and the enamine formof 2-butyl-2-ethyl-1,3-propane diol bis acetoacetate, along with thet-butyl acetoacetate enamine, did not exhibit the characteristic "popand fizz" or the odor of a ketone when opened. In contrast, the othernon-enamine acetoacetates, stored under the same conditions, did exhibitthe characteristic "pop and fizz" and ketone odor when opened,indicating hydrolysis had occurred. The ethyl acetoacetate enaminedestabilized the emulsion in this test.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. The compound 2-butyl-2-ethyl-1,3-propanediolbis(3-amino-2-butenoate).
 2. The compound trimethylpropanetris(3-amino-2-butenoate).